DTC P0108 and Low Vacuum
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Joined: Apr 2010
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From: Jacksonville, AR
DTC P0108 and Low Vacuum
Hi. Little help. Riding last week just crusin' at 55 when the cruise just blipped off and a little sputter from the motor. Reading through the forums I have all the classic symptoms of a bad MAP sensor, so I replaced it. It took some time as all the MOCO dealers were out of stock and I ordered from a third party.
Part got here yesterday and was installed. Nope. Same trouble.
High idle on start and miss and buck when attempting to throttle up. Still throws code as above.
I have checked the output of the MAP sensor while running and I do have a high output just like the DTC says. 2.75 volts at idle but doesn't get much lower when throttled up. If I bump throttle high I see the sensor voltage go down to 1.5 volts and then back up to 4.75 and settle down to 2.75. Pretty normal I'm guessing.
I am thinking that I have a vacuum problem and that the MAP is telling me that.
I have been checking for a intake leak around the manifold but can't pinpoint anything using WD40.
Some of my material that i am reading says that low vacuum could be caused by a cam timing. I haven't checked compression (don't have gauge) yet. I am cautious to open the cam chest as yet as only 5K miles ago I went in and replaced the cam chain tensioners. Thinking they should be okay.
Is it possible that the inner is loose and maybe the chain jumped a tooth?
I dunno. Got to figure out why I have lost vacuum all of a sudden though.
Any thoughts or comments are appreciated.
And then when I get this fixed I can work on the big oil leak from the trans which looks like a main shaft seal. Nice...and I just lost my job last Friday. When it rains it pours I guess.
Part got here yesterday and was installed. Nope. Same trouble.
High idle on start and miss and buck when attempting to throttle up. Still throws code as above.
I have checked the output of the MAP sensor while running and I do have a high output just like the DTC says. 2.75 volts at idle but doesn't get much lower when throttled up. If I bump throttle high I see the sensor voltage go down to 1.5 volts and then back up to 4.75 and settle down to 2.75. Pretty normal I'm guessing.
I am thinking that I have a vacuum problem and that the MAP is telling me that.
I have been checking for a intake leak around the manifold but can't pinpoint anything using WD40.
Some of my material that i am reading says that low vacuum could be caused by a cam timing. I haven't checked compression (don't have gauge) yet. I am cautious to open the cam chest as yet as only 5K miles ago I went in and replaced the cam chain tensioners. Thinking they should be okay.
Is it possible that the inner is loose and maybe the chain jumped a tooth?
I dunno. Got to figure out why I have lost vacuum all of a sudden though.
Any thoughts or comments are appreciated.
And then when I get this fixed I can work on the big oil leak from the trans which looks like a main shaft seal. Nice...and I just lost my job last Friday. When it rains it pours I guess.
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Joined: Apr 2010
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From: Jacksonville, AR
Too technical? I have checked everything I can think of for now. I don't think it is mechanical and the more I thought about it there is no way the cam chain could jump a tooth.
I double checked push rods and lifters and things are normal there. The engine sounds just like it should.
I still get the MAP sensor failure code every time I try to ride it. I have noticed that it will try to throttle up if it is cold, but after a warm up it will backfire on the slightest throttle up.
The svc manual says that I should change the ECM if a MAP sensor replacement didn't fix. Hmm...hope not.
Since I am not the original owner I don't know the history of this. Stage 1 air and pipes with Andrews 21N cams.
Did it require a new ECM map for these additions? If so, is it possible it lost it's program and needs to be re-flashed?
More research more frustration as the HOG sits in the garage.
I double checked push rods and lifters and things are normal there. The engine sounds just like it should.
I still get the MAP sensor failure code every time I try to ride it. I have noticed that it will try to throttle up if it is cold, but after a warm up it will backfire on the slightest throttle up.
The svc manual says that I should change the ECM if a MAP sensor replacement didn't fix. Hmm...hope not.
Since I am not the original owner I don't know the history of this. Stage 1 air and pipes with Andrews 21N cams.
Did it require a new ECM map for these additions? If so, is it possible it lost it's program and needs to be re-flashed?
More research more frustration as the HOG sits in the garage.
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Joined: Apr 2010
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From: Jacksonville, AR
Broken throttle body shaft
Found my problem today. The TPS wasn't keeping up with the MAP as the throttle body shaft was broken in two at the first screw from the TPS.
Of course, the shaft is not available separately but as part of the throttle body @$180 (Zanotti's is $112 which is way better). I am attempting JB Weld and have the # of a good weld shop if that doesn't want to work for me.
So if that fixes the running problem, all I have left is to break open the primary and replace the main shaft seal. Oh....is that all? haha.
Anyone have the tools for that they want to rent?
Of course, the shaft is not available separately but as part of the throttle body @$180 (Zanotti's is $112 which is way better). I am attempting JB Weld and have the # of a good weld shop if that doesn't want to work for me.
So if that fixes the running problem, all I have left is to break open the primary and replace the main shaft seal. Oh....is that all? haha.
Anyone have the tools for that they want to rent?
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Joined: Apr 2010
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From: Jacksonville, AR
Yeah. El Paso is a bit far....but thanks!
The JB Weld is not my friend. Even though I let it cure for 15 hours it cracked as soon as I tried inserting the plate screw.
The welding shop was a life saver though. I took the throttle body to them. They were able to get the shaft out and weld it up nicely for $40. Looks better than new and all the engine problems are gone. (Actually, the throttle feels a little more responsive).
The main shaft leak is a gusher....so on to that I guess.
The JB Weld is not my friend. Even though I let it cure for 15 hours it cracked as soon as I tried inserting the plate screw.
The welding shop was a life saver though. I took the throttle body to them. They were able to get the shaft out and weld it up nicely for $40. Looks better than new and all the engine problems are gone. (Actually, the throttle feels a little more responsive).
The main shaft leak is a gusher....so on to that I guess.
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